GROUND-SOURCE HEAT PUMP CASE STUDIES AND UTILITY PROGRAMS

Transcription

1 GROUND-SOURCE HEAT PUMP CASE STUDIES AND UTILITY PROGRAMS

2 GROUND-SOURCE HEAT PUMP CASE STUDIES AND UTILITY PROGRAMS Paul J. Lienau Tonya L. Boyd Robert L. Rogers Geo-Heat Center Oregon Institute of Technology 3201 Campus Drive Klamath Falls, OR Prepared For: U.S. Department of Energy Geothermal Division 1000 Independence Avenue, SW Washington, DC Administered by INEL Grant No. C ApriI 1995

3 DISCLAIMER STATEMENT This report was prepared with the support of the U.S. Department of Energy, Geothermal Division, administered through Idaho National Engineering Laboratory (INEL) Grant No. C Any opinions, findings, conclusions, or recommendations expressed herein are those of the author(s) and do not necessarily reflect the view of DOE. ACKNOWLEDGEMENTS Data, modeling and analysis for this report were provided by utilities, rural electric cooperatives, equipment manufacturers, universities, end-users and others. Their contributions are gratefully acknowledged. DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the aaurac~. completeness, or usefulness of any information, apparatus, product, Or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, rccommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

4 DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.

5 ABSTRACT Ground-source heat pump systems are one of the promising new energy technologies that has shown rapid increase in usage over the past ten years in the United States. These systems offer substantial benefits to consumers and utilities in energy (kwh) and demand (kw) savings. The purpose of this study was to determine what existing monitored data was available mainly from electric utilities on heat pump performance, energy savings and demand reduction for residential, school and commercial building applications. In order to verify the performance, information was collected for 253 case studies from mainly utilities throughout the United States. The case studies were compiled into a database. The database was organized into general information, system information, ground system information, system performance, and additional information. Information was developed on the status of demand-side management of ground- source heat pump programs for about 60 electric utility and rural electric cooperatives on marketing, incentive programs, barriers to market penetration, number units installed in service area, and benefits.

6 ... TABLE OF CONTENTS EXECUTIVE SUMMARY... Background... Residential Ground-Source Heat Pumps... School Ground-Source Heat Pumps... Commercial Ground-Source Heat Pumps... Economics... Utility Programs... Conclusions and Recommendations... INTRODUCTION... Background... Variables... Performance DATA FORMAT RESIDENTIAL GROUND-SOURCE HEAT PUMPS SCHOOL GROUND-SOURCE HEAT PUMPS COMMERCIAL GROUND-SOURCE HEAT PUMPS ECONOMICS Residential School Commercial Summary UTILITY PROGRAMS Marketing Barriers to Market Penetration Incentives Installations Utility Benefits REFERENCES APPENDIX A: DATA ACCESS... A. 1 APPENDIX B: PARADOX FILE STRUCTURE... B. 1 APPENDIX C: UTILITY GSHP PROGRAMS... C. 1

7 LIST OF FIGURES Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. Figure 12. Figure 13. Figure 14. Figure 15. Figure 16. Figure 17. GSHP performance improvement from 1987 to 1994 for heating mode. GSHP performance improvement from 1987 to 1994 for cooling mode. EER for a GSHP. COP for a %ton GSHP. Types of residential GSHP systems. Residential GSHP system combinations of monitored and simulated data. Residential GSHP annual energy and dollar savings compared to single-zone electric resistance heating with AC in percent. Residential GSHP annual energy and dollar savings compared to air-source heat pumps in percent. Residential GSHP annual energy and dollar savings compared to natural gas furnace with electric AC in percent. Residential GSHP annual energy and dollar savings compared to fuel oil furnace with electric AC in percent. Residential GSHP peak demand reduction compared to single-zone electric resistance heating systems. Type of GSHP system for school applications. School GSHP annual energy and dollar savings. Type of GSHP system for commercial buildings. Combinations of monitored and simulated GSHP systems for commercial buildings. Annual energy and dollar savings for commercial GSHP systems. Residential GSHP simple paybacks compared with conventional energy sys terns.

8 Figure 18. Figure 19, School GSHP system simple paybacks compared with conventional energy systems. Commercial GSHP system simple paybacks compared with conventional energy systems.

9 LIST OF TABLES Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. Table 8. Table 9. Table 10. GSHP Case Study Database Format School Ground-Coupled and Groundwater GSHP Systems Heat Pump Unit Cost (NRECA, 1995) Conventional System Installed Cost (NRECA, 1995) Average Cost Per Ton to Install Ground Loops (NRECA, 1995) GSHP vs. ASHP Electrical Use (kwh) (Kavanaugh, 1992) Break-Even Electrical Rates ($/kwh) For 2-1/2 Ton GSHP vs. 2-1/2 Ton ASHP Implementation Techniques for GSHP Programs (base of 57 programs) Reported Ground-Source Heat Pump Program Rebates Ground-Source Heat Pump Installations by Type

10 GROUND-SOURCE HEAT PUMP CASE STUDIES AND UTILITY PROGRAMS EXECUTIVE SUMMARY Background The purpose of this summary is to present an overview of the findings from 256 case studies of ground-source heat pumps (GSHP), also known as geothermal heat pump installations for residential, school, and commercial buildings. The case studies were compiled into a database that is easily accessible and maintained on personal computers. The database contains information on what data was monitored (metered) or simulated (modeled) and used to establish patterns of energy savings, peak demand reduction and economics for residential and commercial situations. Information was also summarized on the status of demand-side management of GSHP programs for about 60 electric utilities and rural electric cooperatives on marketing, incentives, barriers to market penetration, number of units installed in service areas, and benefits. The savings attributable to the use of GSHP systems in residential, school and commercial buildings vary over a wide range. This variation is the result of a large number of factors that can affect a system's performance. A total of 31 variables have been identified including such parameters as climate, GSHP system type, soil conditions, equipment efficiency, sizing and other issues which influence all GSHP applications. For example in recent years, there has been a substantial increase in the efficiency of GSHP equipment. Based on the performance of a typical machine reported in the American Refrigeration Institute (AN) directory for 1987 and 1994, the average increase in energy efficiency ratio (EER) ranged from 26 to 56 percent, and in coefficient of performance (COP) from 35 to 50 percent. The range is a function of the entering water temperature. Due to these complex variations, the goal was to compare as many case studies of similar data to establish a pattern rather than attempt to remove the variables for an exact comparison. All the case studies evaluated were prepared by other researchers, utilities and manufacturers, and their validity was not investigated. Residential Ground-Source Heat Pumps Residential GSHP systems were documented for 184 case studies which include 24% vertical ground-coupled, 24% horizontal ground-coupled, 2 1 % groundwater, 3% spiral (slinky) and 28% other types. Of these systems, 127 GSHPs were monitored (metered) and compared to 11 1 conventional energy systems of which only 46 were monitored. The average annual energy savings of GSHP systems ranged from 3 1% to 71% and dollar savings ranged from 18% to 54%. 1

11 Residential GSHP Annual Savings Conventional Svstem Electric Resistance Heat/ACa Air-Source Heat Pump Natural Gas FurnacelACb Oil Furnace/ACb Other (propane, unspecified) Number Mean Annual Savings (YO) Energv Number 57% 31% 67 71% 46% Dollars 54% 31% 18% 33% 39% a. AC means with electric air conditioning. b. Natural gas or oil furnaces with electric air conditioning had annual operating costs less than GSHP systems for 23% of the case studies. The mean annual dollar savings of GSHPs shown above may appear attractive; however, due to the relatively low-annual operating costs of conventional energy systems, it is difficult in many cases to recover the additional incremental cost (ground loop) of GSHP systems. Residential GSHP system peak demand reduction compared to single-zone electric resistance heating for 13 case studies ranged from 5.3 kw to 10.4 kw with a mean of 7.2 kw. School Ground-Source Heat Pumps The potential for savings of GSHP systems in schools are documented in 26 case studies which include 54% vertical ground-coupled, 19% groundwater, 12% horizontal ground-coupled, and 15% other types of systems. School GSHP Annual Savings Conventional System Electric Resistance Heat Natural Gas Fuel Oil Number Mean Annual Savings (%) Energy 51% 61% 76% Number Dollars % 58% 3 45%

12 Benefits reported for using GSHP systems in schools are: addition of mechanical cooling, improved control, and simplicity of maintenance and repair. In southern climates, the benefits include: elimination of cooling towers, outdoor equipment, mechanical rooms and ductwork. Commercial Ground-Source Heat Pumps Case studies (46) documented for commercial GSHP systems ranged in capacity from 30 to 4,700 tons. These systems employed vertical ground-coupled (43%), groundwater (35%), horizontal ground-coupled (1 1%) and other (1 1 %) types of ground systems. Commercial GSHP systems were monitored in 84% of the case studies, and conventional energy systems is only 20% of the comparisons. The average annual energy savings of GSHP systems ranged from 40% to 72%, and dollar savings ranged from 31% to 56%. Commercial GSHP Annual Savings Conventional System Electric Resistance Heat/AC Air-Source Heat Pump Natural Gas Fuel Oil Mean Annual Savings (%) Number Energy Number Dollars 6 59% 5 56% 3 40% 3 37% 4 69% 4 49% 6 72% 7 31% The savings attributable to the use of GSHP systems in commercial buildings vary over a wide range. In addition to parameters common to all GSHP applications, unique to commercial buildings are building use, internal heat gains and more complex rate structures. Predictions of savings to be achieved with a GSHP system are a very site-specific endeavor for commercial buildings. Economics The economics of residential GSHP were reported as simple paybacks in only 15% of the 184 case studies. A favorable simple payback is considered to be less than 5 years. Residential GSHP system simple paybacks ranged from 1.4 to 24.1 years, and the mean was 7.0 years. 3

13 Residential GSHP Economics ~ Conventional System Number Electric Resistance Heat/AC Air-Source Heat Pump Natural Gas/AC Fuel Oil/AC Other ~~ Simple Payback (yrs) Range Mean 2.7 to 2.0 to 4.2 to 1.4 to 2.0 to The biggest barrier to faster paybacks of GSHP systems is the incremental cost of the ground loop. Since residential GSHP systems are usually included in the mortgage, a break-even value of electric rates is a more meaningful value than simple payback. In January 1995, data became available on the cost of purchasing and.installing residential GSHP systems. Based on this data, an earlier analysis of a new well insulated home and a 30year fixed rate mortgage at 8%, the electrical break-even rates were calculated for two different climate zones. In the colder zone, the break-even rates were $O.O6l/kWh for vertical and $O.O58/kWh for horizontal ground-coupled systems. In the warmer zones, they were $0.097 and $0.084 respectively. Electric rates in excess of these break-even values would result in the GSHP system having a positive cash flow to the homeowner. Details on this analysis are presented in the economic section of this report. Simple paybacks for school systems were reported in only 5 out of 23 case studies. These simple paybacks ranged from 5 to 14 years for electric resistance heating, 3.5 years for natural gas system, and 5 to 7 years for others. Case studies for commercial buildings reported simple paybacks for 17 out of 46 GSHP systems. The range of simple paybacks was 1.3 to 4.7 years with a mean of 2.8 years. For commercial buildings, all but 4 of the simple paybacks represent buildings located in northern climates. Caution should be used in arriving at economic conclusions for any of the three groups presented in this summary. This is due to variables of climate, ground characteristics, GSHP system type, equipment efficiency, sizing, complex utility rate structures, and a variety of economic analysis methods used in the case studies. 4

14 Commercial GSHP Economics Conventional System Electric Resistance Heat Natural Gas Fuel Oil Other Number Range Mean Years Years When considering a GSHP system for either new or retrofit situations, it is imperative that a deliberate economic analysis be performed. Utility Programs Ground-source heat pumps (GSHP) are one of many technologies utilities are considering or implementing for demand-side management (DSM), especially aimed at improving the efficiency with which customers use electricity. Information was developed on the status of DSM programs for GSHPs including: utility/contacts, marketing, barriers to market entry, incentives, number of units installed in service areas and benefits. A total of 57 utilities and m a l electric cooperatives out of 178 investigated were reported to have DSM programs involving GSHPs. Marketing techniques employed by utilities included utility publications and seminars (36%), newspaper and radio/tv advertising (16%), test/demonstrations (1O%), education (6%), home shows (6%) and other (26%). The primary market penetration barrier cited by utilities was the first cost of installation of GSHP systems, especially the incremental cost (median cost of $700 to $900/ton of the ground loop. Other barriers include low-annual cost of natural gas, lack of manufacturers, dealers and loop installers, customer resistance to heat pump technology, and regulatory problems. Utilities have designed a number of incentive packages to encourage the installation of GSHPs. The most common are cash rebates to customers (mean values of $208/ton and $382/unit) and trade ally ($200/ton). In many cases, the utility specifies a minimum Seasonal Energy Efficiency Ratio (SEER), usually 10 or greater, energy audits or minimum insulation standards. Other types of incentives include special financing, discounted energy rates, and free ground loop installation. More than 18,800 GSHP systems (3-ton equivalent) were reported by 35 utilities out of the 57 contacted. The types of systems installed include: horizontal ground-coupled (46%), undefined systems (40%), groundwater systems (7%) and vertical ground-coupled (7%). 5

15 A total of 25 utilities reported some type of benefit from the installation of GSHPs. Most of the utilities (76%) reported that peak demand reduction (peak shaving) was the primary benefit. Other benefits include: annual load reduction, higher load factor, higher winter efficiency, environmental benefits, competitive with other fuels, maintenance free and customer satisfaction. Conclusions and Recommendations Residential ground-source heat pumps are an effective approach to reduce both consumer energy consumption and electric utility peak loads. Demand reduction occurred primarily on the heating side. The savings attributable to these systems varied over a wide range (energy at 3 1'YO to 71% and dollar at 18% to 54%), due to the many factors that affect their performance and economics. The GSHP industry has been primarily involved in the residential sector and has been most successful in areas characterized by winter peaking utilities, moderate electric rates and moderate to severe winter heating requirements. Although annual dollar savings appear attractive, especially for residential GSHP systems, the large incremental cost of these systems makes it essential that an economic analysis be performed. Marginal or negative economics occurred in areas of low electric rates or widely available natural gas. Software is available from manufacturers and independent sources to predict residential system performance and economics for specific conditions, given input on ground characteristics and climate. Case studies of school and commercial building GSHP performance and economic results were less conclusive than those for the residential sector. Given all the potential influences upon school and commercial building energy use, predictions of savings to be achieved with a GSHP system becomes a very site-specific endeavor. There is a need to further document information on operating experience of school and commercial GSHP systems and report on success andor failure at various locations in the United States. 6

16 INTRODUCTION Background The Department of Energy (DOE) and the Environmental Protection Agency (EPA) are rapidly expanding their involvement in programs to promote increased use of both renewableenergy resources and energy-efficient technology. Federal implementation of the Clean Air Act Amendments of 1990 and the Energy Policy Act of 1992, and other regulations still under development are a result of an increasing worldwide environmental consciousness. Further, the environmental and efficiency aspects of energy production and use are expected to remain top priority items in President Clinton s Administration. Geothermal heat pump (GHP) systems can help meet the challenge by increasing our energy efficiency, with resulting benefits to utilities in better load management, to customers in lower utility bills and to society in a cleaner environment (Pratsch, 1992). The purpose of this study was to: 1) determine what existing monitored data (metered) are available on ground-source heat pumps (GSHP) installations, also known as geothermal heat pumps, for residential, school and commercial buildings, 2) determine seasonal energy use, savings patterns and economics of ground-source heat pump systems, with competing energy systems in typical residential and commercial situations, and 3) develop information that will include electric utility marketing, incentive programs, barriers to market penetration, number of installations in utility service area, and benefits to utilities. Electric utilities are the ultimate market target for GSHPs, especially utilities which are already committed to demand-side management (DSM). A utility in its resource planning process, the Planning Director s recommendations to management must be consistent with prevailing energy policies and supported by data. The data must show that the resource and technology are available, reliable, and cost competitive with other options. Concerns of utilities considering GSHP technology as a DSM option include: 0 Demonstrated efficiency and energy/demand savings; High first cost of ground loop and wells; Effect of ground loop temperature increase for summer and long-term operation, especially for commercial applications; Utility rebates and other incentives; Infrastructure availability of heat pump dealers and loop installation contractors; Regulatory and public acceptance; and End-user satisfaction. Data on GSHP systems were organized into case studies and compiled into a database. All the case studies evaluated in this report were prepared by other researchers, utilities and manufacturers and their validity is not investigated. 7

17 Variables. The comparisons made by the case studies must be qualified by the variables that affect their operating performance. For example, heat pump efficiencies for all energy systems vary significantly according to type of equipment and operating conditions. The energy requirements of the location vary according to the outside air conditions and the envelope of the structure. Due to the complex variations that affect a system s performance, it is very difficult to exactly compare two different applications. It is the goal of this report to compare as many case studies of similar data to establish a pattern rather than attempt to remove the variables for an exact comparison. The following is a list of variables that are considered significant in evaluating GSHP systems. Variables in Performance of GSHP Systems Climate conditions Ground conditions - soil conductivity, moisture content, soil diffusivity Length of loop Type of loop - vertical, horizontal, or spiral Type of equipment - COP, EER Capacity of the heat pump (sizing) Type of system - groundwater, ground-coupled, lake loop, etc. a Variables in Monitored Data Monitoring equipment Locations monitored Time data were collected Monitored data classified into two types: Basic parameters: Heat pump power (kw) and energy (kwh)) Supply and return ground-loop temperatures Flow in ground-loop, a one-time measurement Comprehensive parameters: Ground-loop pump power (kw) and energy (kwh) Fan power (kw) and energy (kwh) Air flow Ground temperatures of various distances from the ground-loop Air supply and return temperatures Space and outside temperatures Run-time 8

18 ' Comparative modeling techniques Reliability of data Collection procedures Data analysis techniques Continuity of data (gaps) Performance Variables in Monitored Systems (buildings) Building usage - people/schedule Operation Orientation Climate conditions Equipment performance Type of installation Installers expertise Control system - set pointddead bend Variables in Theoretical Studies Weather modeling Equipment modeling - EER, COP, gas furnace efficiency (AFEU), etc. Financial assumptions - interest Internal gain assumptions Envelope assumptions - air change role The energy performance of a GSHP system can be influenced by three primary factors: the heat pump machine, the circulating pump or well pump, and the ground-coupling or groundwater characteristics. The heat pump is the largest single energy consumer in the system. Its performance is a function of the two things: the rated efficiency of the machine and the water temperature produced by the ground-coupling (either in the heating or cooling mode). The most important strategy in assembling an efficient system is to start with an efficient heat pump. It is difficult 'and expensive to enlarge a ground-coupling to improve the performance of an inefficient heat pump. Water-source heat pumps are currently rated under one of three standards by the American Refrigeration Institute (AM). These standards are AM-320, AM-325, and ARI-330. The standard intended for ground-coupled systems is AM-330 entitled "Ground Source Closed Loop Heat Pump Equipment." Under the standard, ratings for cooling EER and heating COP are published. It's important to consider that these are single-point ratings rather than seasonal 9

19 ~ GSHP Performance g / I I I I I i I Entering Water Temperature, F L-m =1987 ]?igure 1. GSHP performance improvement from 1987 to 1994 for heating mode I 8 I I = Entering Water Temperature, F Ggure 2. GSHP performance improvement from 1987 to 1994 for cooling mode. 10

20 values as in the case of air-source equipment. Cooling EER values are based on an inlet water temperature of 77 F. Heating COP values are based on a heating inlet water temperature of 32 F. These values are characterizations of a northern climate. The current ARI directory contains equipment with EER ratings of less than 10 to a high of COP values range from 2.8 to 3.6. It is evident that there is a wide range of equipment performance at the standard rating conditions. Based on these values, it is evident that the performance of the equipment can vary by as much as 100% according to the quality of heat pump purchased. In recent years, there has been a substantial increase in the efficiency of GSHP equipment. Based on performance reported in the ARI directory for 1987 and 1994, the increase in EER ranges from 26 to 56 percent, and in COP from 35 to 50 percent depending on the entering water temperature. Figures 1 and 2 show this increase in performance for a typical machine based on average values of EER and COP as a function of entering water temperature. Based on improvements in performance of GSHPs from 1987 to 1994, the date of a GSHP installation should be noted. In this report, values for energy savings, demand reduction, etc., are those reported in the case studies, some of which were fiom the early 1980s. The actual performance of the equipment is a function of the water temperature produced by the ground-coupling. The values discussed above are based on standard rating conditions (77'F cooling and 32 F heating). The actual temperatures are a function of the local ground temperatures and the design of the ground-coupling. For example, in a region where the local ground temperature is 60 F and the ground loop is designed for the customary 20" to 25 F aboveground temperature, a heat pump rated at an EER of 16.8 would actually operate at an EER of 14.2 under peak load conditions. A poorly designed loop, which forced the unit to operate at 30 F aboveground temperature, would reduce the value to less than These examples are for cooling operation which is the dominant load in commercial applications. The same relationship holds for heating operations, however. Figures 3 and 4 show EER and COP as a function of inlet temperatures for a 3-ton machine designed for ground-coupled applications from a manufacturer's specifications. The system energy performance is also influenced by the pumping energy required to circulate the fluid through the heat pump and the ground loop. One author (Kavanaugh, 1994) in the design of ground-coupled systems suggests the following guidelines for pumping power for commercial ground-coupled systems: Efficient systems: (50 watts/ton Acceptable systems: watts/ton Inefficient: >lo0 watts/ton I1

21 EER vs EWT I Entering Water Temperature, (F) Ggure 3. EER for a %ton GSHP COP vs. EWT 5.5 _ Entering Water Temperature, (F) Figure 4. COP for a 3-ton GSHP 12 80

22 To put these values into perspective, consider an office building with a 50-ton cooling load,and heat pump units selected to operate at an EER of 14 under peak conditions. With an efficient circulating pump design (35 watts/ton), the energy demand of the circulating pump would amount to (50 tons).(35 wattslton) = 1750 watts. Combining the pump demand with the heat pump unit demand results in a system EER of The same building and equipment coupled to a poorly designed pumping system consuming 120 watts (6000 watts pumping power) per ton would yield a system EER of only 12.2; thus, compromising the premium paid for the higher efficiency equipment. As indicated above, coupling this system to an inadequate ground-coupling could easily reduce the system EER to between 10 and 11. In summary, it is necessary when evaluating a ground-coupled system to consider the efficiency of the machine, the adequacy of the ground-coupling and the nature of the pumping design to hlly understand the efficiency of the system. 13

23 DATA FORMAT ' The case studies that appear on the enclosed 3-1//2 inch diskette were compiled into a database. The ground-source heat pump (GSHP) database was designed to be readily accessible and maintained on personal computers. The source data were entered into Paradox version 5.0 database containing 65 data fields. The field names, general descriptions of their contents and explanation of codes are listed in Table 1 and shown on the form "Case Study." The form can be accessed by sohare Paradox 5.0 or Wordperfect 6.0. The source data (on Paradox 5.0) can be accessed using the following software: Wordperfect 6.0 Quattro Pro 5.0 and 6.0 Microsoft Excel 4.0 and 5.0 Micrsoft Word 6.0 and 2.0 Instructions on how to access, view and update the source data on either a form or table are given in Appendix A. Appendix B contains the Paradox file structure for the fields in the main file CASESUM2. db. Table 1. GSHP Case Study Database Format Field Name Ref. No. Reference Description Identification number assigned to each case study, state - reference number m. A reference number followed a lower case alpha denotes a system where more than one was analyzed. CN, GR and a SW denote Canada, Germany, and Sweden. Source of data. General Information Type of Installation Date Installed Building Size Location Identified as a residential, school or commercial building. Date of GSHP installation. Area in square feet. Location of where heat pump is installed. 14

24 System Information System Description Type Construction Design Temperature HDD CDD Capacity Heat Pump Manufacturer Monitored Data Description of building and its characteristics. Identified as a new or retrofit. Outdoor dry-bulb design temperature. Heating degree days. Cooling degree days. Heating or cooling capacity of heat pump in tons. Equipment manufacturer. Identifies system components that were instrumented and monitored (i.e., compressor, circulating pump, fans, loop temperature, flow in ground loop, ground temperatures, air temperatures, space and outside temperature, and run-time). Ground System Information Ground Heat Exchanger Configuration Ground Temperature Pipe Material Pipe Size Description of ground loop or groundwater system. Temperature of ground or groundwater in degrees Fahrenheit. Type of pipe material used for closed loop. Diameter of loop pipe in inches. Vertical Number of Boreholes Borehole Depth Number of boreholes drilled. Well depth in feet. 15

25 Horizontal Trench Length Trench Depth No. of Pipes Length of trench excavated for horizontal loop in feet. Depth in feet. Number of pipes in trench. Groundwater Number of Wells Depth of Well Casing Diameter Flow Rate Number of production and injection wells. Depth in feet. Diameter in inches. Total flow rate from all wells in gpm. System Performance Ground-Source Heat Pump System Type Data Run-Time Heating Run-Time Cooling Annual Energy Usage Percent Energy Savings COP EER Total Installed Cost Annual Operating Cost Percent Dollar Savings Monitored (metered) or simulated (modeled). Number of hours per year heat pump operated in the heating mode. Number of hours per year heat pump operated in the cooling mode. Annual energy required to operate the heat pump in kwh. Annual energy savings of GSHP compared to specified conventional energy in percent. Coefficient of performance. Energy efficiency ratio. Cost of installed GSHP system including ground loop or wells. Annual cost to operate the GSHP system. Annual dollar savings of GSHP system compared to conventional system in percent. 16

26 Payback Period Time to payback GSHP system from savings over conventional energy system in years. Conventional Energy System Type Data Air-Source Heat Pump Electric Heat Natural Gas Fuel-Oil Annual Energy Usage Conventional Annual Conventional Cost Monitored (metered) or simulated (modeled). Annual energy required to operate air-source heat pump system in kwh. Annual energy required to operate an electric resistance heating system in kwh. Annual energy required to operate a gas furnace in Therms (lo5 Btu or 1 ccf). Annual energy required to operate an oil-fired system in gallons. Annual energy of any of the above four systems converted to kwh. Annual cost to operate a conventional system in dollars. Additional Information Contact Person Location Phone Number Person who furnished data or contact for additional information. Address of contact person. Phone number of contact person. 17

27 CASE STUDY GROUND SOURCE HEAT PUMPS OIT Geo-Heat Center 3201 Campus Drive Klamath Falls, Or (503) 885- I750 Type of installation: FIELDUype of installation) Building size (square fi): FIl$D(Building size (sq.ft.)) State: FIELD( State) Ref No. s g p e f No.1) Reference FEED'(Reference) GENERAL INFORMATION Date Installed: FIELD(DATE INSTALLED) Country: FIELD(Country) Zip: FIELD(Z1P) SYSTEM INFORMATION System description: FIELD(System description) Design temp.: FELD(Design temperature) OF Type Construction: New: FIELD(New) Retrofit: FIELD(Retrofit) CDD: FIELD(Coo1ing deg days) Circ. Fluid: FIELD(Circ. Fluid) HDD: Fl@g(Heating deg days) Heat pump manufacturer: FIELD(Heat pump manufacturer) Capacity: cij.$d{capacity) tons Monitored data: FIELD(Monitored data) GROUND SYSTEM INFORMATION Ground heat exch. config: FIELD(Ground heat exch. config.) Ground temp.: EJI$GD(Ground temperature) OF Pipe material: FSELQ(Pipe material) Pipe size: R i G Q P i p e size) in. VERTICAL GROUND COUPLED: Number of boreholes:feldo\lumber of boreholes) Borehole depth: FIELD(Boreho1e depth) ft. HORIZONTAL GROUND COUPLED: Trench length: FI@D(Trench length) ft No. of pipes: FIELD(N0. of pipes) Trench depth: FIELDPrench depth) ft GROUND WATER: Number of wells: FELDO\lumber of wells) Casing d i m. : FIELD(Casing d i m. ) in Depth of well: FIELD(Depth of well) ft Flow rate: FJELD(Flow rate) gpm SYSTEM PERFORMANCE GROUND-SOURCE HEAT PUMP SYSTEM: Type of Data: Monitored: FIELD(Monitored GSHP) Simulated: FIELD(Simu1ated GSHP) Runtime heating: FIELD(Runtime heating) hrs, Runtime cooling: FIELD(Runtime cooling) hrs COP: FIELD(C0P) EER: FIELD(EER) Annual energy usage: FIELD(Annua1 energy usage) kwh Percent energy savings: FIELD(Percent energy savings) Total installation cost: $ FIELD(Tota1 installation cost) Annual operating cost: $ FIELD(Annua1 GSHP cost) Percent dollar savings: FIELD(Percent dollar savings) Payback period: FIELD(Payback period) years CONVENTIONAL ENERGY SYSTEM: Type of data: Monitored:FIELD(Monitored conventional) Simulated: FIELD(Simu1ated conventional) Air-source heat pump: FIELD(Air-source heat pump) k W h Electric heat: FIELD(E1ectric heat) kwh Natural gas: FIELD(Natura1 gas) Therms Fuel-oi I FIELD(Fue1-oi I) gal Ions Annual energy usage conventional: FIELD(Annua1 energy usage conv ) kwh Annual conventioanal cost: $ FIELD(Annua1 Conv. cost) ADDITIONAL INFORMATION Contact person: FIELD(Contact person) Address FIELD(Address) Country: FIELD(Countr)') Zip FIELD(Zip') City FIELD(City') State FIELD(State') Phone number: FIELD(Phone number) FIELD(Page) 18

28 RESIDENTIAL GROUND-SOURCE HEAT PUMPS Households use about one-fifth of the primary energy consumed in the United States (including the energy required to produce electricity and deliver it to final users). Space heating accounts for the largest single share of primary energy use in the residential sector for the nation as a whole at about 36%, followed by water heating at 15%, refrigerators at 12%, space cooling at lo%, etc. (NES, 1992). Residential electric space heating can potentially help both summer or winter peaking utilities achieve several load shape modification objectives. A utility may make strategic conservation and peak reduction investments by promoting efficient heat pumps to replace resistance heaters (or less efficient heat pumps). To determine the potential of ground-source heat pump (GSHP) systems to satisfy these objectives, existing monitored data and other information was collected from electric utilities, rural electric cooperatives, manufacturers, engineers, universities and other sources. A total of 184 residential GSHP case studies are summarized on the enclosed inch diskette. These systems represent GSHP installations that are groundwater, ground-coupled (vertical, horizontal and spiral) or others. Others comprise unspecified ground systems or lake loops (2). Figure 5 shows the types of GSHP systems in the database. The type of data entered could be either monitored (metered) or simulated (modeled) for residential GSHP and conventional energy systems. GSHP systems were monitored for 128 out of the 184 case studies. Conventional systems were monitored for only 46 out of 11 1 systems. Conventional systems could include electric resistance heating, air-source heat pumps, natural gas furnace with electric air conditioner (AC), oil furnace with electric AC, and others. These conventional systems were compared to GSHP systems for energy savings patterns, power reduction for electric resistance (heating only), operating costs, etc. Figure 6 shows the number of combinations of monitored and simulated systems in the database. A number of factors influence the performance of GSHP systems. These are identified in the introduction of this report. Important factors associated with residential GSHP systems are those that affect the performance in one locality apart from another, climate and ground characteristics. In addition, the efficiency of the equipment has improved considerably in recent years; therefore, the date of installation may reflect these improvements. The sizing of the ground loop to the machine relative to the load are important factors influencing performance that is affected by run-hours. The type of ground system employed is also an important consideration. The following graphs showing energy savings patterns and peak demand reduction do not attempt to separate all of the variables, except for the locality identified as a reference number for the state where the system is located. 19

29 Number of Residential GSHP Systems Figure 5. Types of residential GSHP systems. Residential GSHP Systems GSHP simulated / Conv. System monitored (7) GSHP monitored I Conv. System simulated (19) Monitored alone GSHP and Conv. System simulated (46) Simulated alone (:31 GSHP and Conv. System mo Figure 6. Residential GSHP system combinations of monitored and simulated data. 20

30 A more detailed assessment of the performance on specific systems can be obtained by referring to specific case studies summarized on the diskette or the reference fiom which the data was obtained. Figures 7 through 10 show patterns of annual energy and dollar savings of residential GSHP systems compared to electric resistance heating, air-source heat pumps, natural gas furnace with electric air conditioning (AC), and oil fired furnace with electric AC. The mean annual dollar savings of GSHPs compared to electric resistance heating is 54% and for air-source heat pumps it is 3 1%. Due to the high first cost of GSHP systems, mainly because of the additional incremental costs of the ground loop, economics is an important issue. Even though the percent dollar savings may appear attractive, because of relatively low annual operating costs of conventional systems, it is difficult to recover the additional incremental cost of the GSHP systems. The economics section of this report addresses this problem. In the cases of comparing natural gas and oil furnaces with electric air conditioning, there were five case studies where the conventional systems had annual operating costs less than GSHP systems. When considering a residential GSHP system for either new or retrofit situations, it is imperative that a deliberate economic analysis be performed. Peaking performance improvements of GSHP systems can be evaluated as a coincident peak that occurs at the time of the utility peak. A non-coincident peak OCCUTS at the time of the greatest difference between the GSHP system load and the competing systems load. Figure 11 shows winter non-coincident peak demand reduction of GSHP systems compared to single-zone electric resistance heating systems. For these 13 systems, the range was from 5.3 to 10.4 kw with a mean of 7.2 kw. 21

31 Residential GSHP vs Elec. Res. Heat 1oc Percent Annual Energy Savings 80 x F 60 Q) G Q) Residential GSHP vs Elec. Res. Heat 80 Percent Annual Dollar Savings Figure 7. Residential GSHP annual energy and dollar savings compared to single zone electric resistance heating with AC in percent. 22

32 Ground Source vs Air Source Heat Pump Percent Annual Energy Savings 100 % c > 80.d gx f& 20 8c 5 s 0 CT43h CTd32d GA-5371 GA-553 LS37f KYdl7 MN.018 Ms-137 NJ-547 Ref. No. NY-303b OHM12 OR4371 ORol'lb PA-131 PA-YSb PA-YY Ground Source vs Air Source Heat Pumps Percent Annual Dollar Savings =a0 20 c 0 0 a c, s a ,.lad,, I,, I, b / I, %A-JI~ ' I L - J ~ k y d 'MN418' 'NJ-547' kumd b~d17; RM7d PA-%%' ba-% GAJ37a ILJ37d KY.017 L~436c MN.019 NY-103b OHMla OR471 PA-5451 PA-YSc Ref. No. Figure 8. Residential GSHP annual energy and dollar savings compared to air source heat pumps in percent. 23

33 GSHP vs Natural Gas 3 Percent Annual Energy Savings 80 % I c 60 >.d 2 c-r 2 20 Q) pc 0 CA-30Sa CA-3OSb ( 'CA-305; c - -Kef. N o LS-302 f ' IL-537c GA-537b :Y-S38a NJ-03Sa - NY-O2Sc OK-027 GSHP vs Natural Gas 80 I IR-037b IY-3038 Percent Annual Dollar Savings % I r: a -~ -_._ ~~... ~. c~~~ ~....~~. ~ - ~. AL-306a AL-306~ AL-536 CA-305b CA-30Sc IL-537; LA-036b LS-302 NY.303, OK-027 VA-548 AL-306b AL-306d CA-30Sa CA-30Sc GA-537b KY-538a LA-036d NY-303c OH-Mid OR-037b Ref. No. Figure 9. Residential GSHP annual energy and dollar savings compared to natural gas furnace with electric AC in percent. 24

34 GSHP vs Fuel Oil Percent Annul Energy Savings 80 0 NY428C OH44lc PA-029b Ref. No. GSHP vs Fuel Oil Percent Annual Dollar Savings =0a a II CN-OSOa ' CN-OSOc I GR-308a ' GR-308~ I GR-308d Ref. No. NY-303f ' OH-041~ ' OR-037d Figure 10. Residential GSHP annual energy and dollar savings compared to fuel oil furnace with electric AC in percent. 25

35 Residential GSHP vs Elec. Res. Heat Peak Demand Reduction CN-052a Figure 11. I CN452c CN-052d.- CN-O52c ID423 LA436a Ref. No. NE426 NY Residential GHP peak demand reduction compared to single-zone electric resistance heating systems. 26

36 SCHOOL GROUND-SOURCE HEAT PUMPS The potential for energy savings in schools using GSHP systems is demonstrated in the 26 case studies on the enclosed diskette. Figure 12 shows the number of types of school systems documented. School GSHP systems were monitored for 23 of the 26 systems reported; three systems were simulations. Annual energy savings were reported for only 6 schools, shown in Figure 13. Five case studies reported percent annual dollar savings (Figure 13) and the remainder (1 7) were monitored alone without comparisons to conventional systems. The largest school GSHP project is the 1,480-ton Richard Stockton College of New Jersey system in Pomona (NJ-074). This is a vertical ground-coupled system consisting of 400 boreholes, each drilled to 400 ft and located under a parking lot on 15 ft grids. The system was monitored for baseline data prior to the installation of the GSHP system and continues to be monitored since the GSHP system started operating in January Figure 12. Type of GSHP system for school applications. 27

37 Percent Dollar Savings 0 h, 0 P o\ Percent Energy Savings c , 0, I I, ' 0 I I l I I t i t t i E? vl W N c, I I I I I I I m P h, I I I, ' 0 1, / 00, 0. ) I ( CL 0 0

38 In Austin, Texas, 48 elementary schools, 4 middle schools and 3 community colleges have been equipped with GSHP systems with a total installed capacity of 6,600 tons (TX-072). A total of 6,373 vertical loops were installed from with 1,266 miles of pipe at an average depth of 270 ft/ton. Table 2 shows a comparison for two different types of school GSHP systems. The first is a middle school in Wahpeton, North Dakota (ND-066), employing a vertical ground-coupled system and the second is a high school located at Junction City, Oregon (OR-075), employing a groundwater system. Table 2. School Ground-Coupled and Groundwater GSHP Systems. School: Installed Date: System: Application: Design Condition: Capacity: Energy: Installed Cost: SavingsNr: a. Heating degree day b. Calculated Wahpeton, ND boreholes (150 fi) Middle school - 57,400 fi HDDa, -25 F 220-tons 678,000 kwyr $41 8, ,800 therms of gasb Junction City, OR 1988 Productiodinjection wells High school - 55,300 fi? 4793 HDD, 17 F tons 193,133 kwyr $265,000 35,506 therms of gas In the case of the North Dakota school, there is three times the energy savings over the Oregon school due primarily to the fact of being located in a much colder climate. Benefits reported for using GSHPs in schools include: addition of mechanical cooling, improved control--being able to condition a very small area without having to condition the entire school, and simplicity of maintenance and repair. In southern climates, the elimination of cooling towers, outdoor equipment, mechanical rooms and ductwork were added benefits. In most cases, there were reduced maintenance costs, energy savings and peak power reduction. 29

39 COMMERCIAL GROUND-SOURCE HEAT PUMPS ' Case studies (46) documented for commercial GSHP systems on the enclosed diskette ranged in capacity from 30 to 4,700 tons. These systems employed ground-coupled well fields of up to 370 boreholes for an 850-ton system (OK-078) to 3 wells for a 4,700-ton groundwater system (KY-077). Figure 14 shows the number of types of commercial GSHP systems documented. Figure 15 shows the number of commercial GSHP and conventional systems that were monitored and simulated. Annual energy savings for commercial GSHP systems were compared to 19 conventional energy systems and dollar savings for 19 systems, as shown in Figure 16. In the past, some have attempted to extrapolate the savings of GSHP systems from residential to commercial applications. This is not a valid approach. Even comparing savings among commercial buildings themselves is a difficult task. It is apparent from Figure 16 that savings attributable to the use of GSHP systems in commercial buildings vary over a wide range. This variation is the result of a host of factors some of which have been discussed above. In addition to such parameters as climate, GSHP system type, soil conditions, equipment efficiency, sizing and other issues which influence all GSHP applications, unique to commercial buildings are building use, internal heat gains and more complex utility rate structures. Commercial building HVAC loads are heavily influenced by the nature of businesses occupying them. Retail establishments tend to have high lighting loads, offices have moderate lighting with high equipment and occupant loads. These internal heat gains tend to raise air conditioning loads and reduce heating loads. This effect is magnified as the size of the building increases. As a result, space heating requirements, in large retail and office buildings are low in terms of Btu/ft*.yr relative to residences and other types of commercial buildings. Hotel and motel buildings, due to their 24-hour occupancy and domestic hot water loads, tend to have higher heating requirements than retail and office buildings. Retirement, nursing and similar medical-residential facilities also are characterized by high heating requirements. For applications in which only space conditioning is done, higher heating requirements tend to generate higher savings for GSHP systems. A few ground source systems have been installed in small convenience store retail facilities. Although heating requirements may be small in such facilities, savings generated through connection of the display refrigeration equipment to the ground loop can generate substantial savings due to the 24-hour operation of this equipment. 30

40 Vertical (20) Groundwater Horizontal ( 5 ) Figure 14. Type of GSHP system for commercial buildings. Commercial GSHP Systems GSHP monitored / Conv nitoired all le X H P a.nd Conv. System GSHP and Conv. System monitored ( one (1) Figure 15. Combinations of monitored and simulated GSHP systems for commercial buildings. 31

41 Commercial GSHP vs Conv. Systems 100 Percent Annual Energy Savings, MS-06(a CA443b ASHP CA443a CN-503 CN-SO4 Ref. No. CN-SI0 GR-SISa Elec. Res. Heat GR-SISc Fuel Oil Commercial GSHP vs Conv. Systems *O Percent Annual Dollar Savings i ASHP EElec. Res. Heat Fuel Oil Figure 16. Annual energy and dollar savings for commercial GSHP systems. 32 CN-So6

42 In addition to the internal, occupancy and process loads, commercial building energy use can also be influenced by the shape and orientation of the structure, quantity of ventilation air, presence or absence of heat recovery and a host of other parameters. By influencing loads, these factors also affect savings to be achieved by more efficient HVAC system. Beyond the loads imposed on the system, there is consideration of more complex utility rates generally used for commercial buildings. In residences, customers are billed only for the energy (kwh) used. In commercial buildings, the customer is billed for the energy used in terms of kwh, but also for the peak rate (kw) at which he uses that energy. This is called a demand charge. The time period over which the demand is calculated and the portion over which it is applied influences the cost of operation. Some utilities are moving towards time-of-day rates which alter the kwh charge according to period of the day in which the electricity is consumed. Because the electricity rates and the way they are applied vary from utility to utility, they can have a profound effect upon savings. It is clear that given all the potential influences upon commercial building energy use, prediction of savings to be achieved with a GSHP system becomes a very site-specific endeavor. 33